In-tank cleaning articles that codispense both detergent and disinfectant cleaners are well known. See, for example, U.S. Pat. No. 3,504,384 to Radley, et al.; U.S. Pat. No. 4,208,747 to Dirksing; and U.S. Pat. No. 4,212,016 to Wages. Although nonhypohalite disinfectants may be employed as the disinfectant constituent in such codispensing articles, disinfectant tablets releasing hypohalite ions, preferably hypochlorite ions, are greatly preferred in terms of effectiveness, ease of manufacture, cost, delivery, and the like.
It is also preferred that the cleaner article deliver a dye to the bowl water, the presence of the dye indicating that the article is working and that the active materials have not been used up. In addition, the presence of a color in the bowl water is aesthetically pleasing to consumers, who have in the past demonstrated a preference for a blue tint or color of the bowl water.
U.S. Pat. Nos. 4,200,606 and 4,249,274, both to Kitko, disclose that the triarylmethane dyes FD&C Blue No. 1 (Colour Index Dye No. 42,090) and FD&C Green No. 3 (Colour Index Dye No. 42,053) are "stable" to hypochlorite ions under conditions stated therein. Thus, the color provided by FD&C Blue No. 1 is stated to be persistent when the bowl water hypochlorite ion concentration measured as available chlorine is between 2 to 10 ppm, when the dye concentration is between 0.5 to 5 ppm, and when the bowl water pH after a flush is from about 8 to about 9.5, the ratio of available chlorine to dye being from about 2:1 to about 6:1. At the same concentrations of disinfectant and dye, and at the same ratios thereof, FD&C Green No. 3 is stated to provide a persistent color when the pH of the bowl water after the flush is from about 8.5 to about 9.5. Unlike many dyes and unlike pigments, these dyes are not substantive to porcelain, and do not stain the bowl.
Although stated to be resistant to attack by hypochlorite ions, including hypochlorite ions formed by dissociation of chlorinated hydantoin compounds and trichloroisocyanuric acid, the Colour Index Dye No. 42,090 has, in fact, been found to be unsuitable for use in combination with these particular disinfectants. The water supplied to toilets has quite variable pH, depending on geographic location, ranging generally from between about 6.5 to about 10. In the case of trichloroisocyanuric acid, the delivery of this disinfectant to the bowl water lowers the pH of the water, in view of its acidic nature. Moreover, it has been found that trichloroisocyanuric acid undergoes, in aqueous solution, a slow dissociation to form chloramines and other nitrogen containing species. It is believed they attack the triarylmethane structure of the aforementioned dye. Formation of chloramines is believed to also occur with non-nitrogen containing disinfectants, for example, calcium hypochlorite, in the presence of ammonium ions, which ions are present in some water systems. Hence, in aged trichloroisocyanuric acid solutions containing its dissociation species, the C.I. Dye No. 42,090 has been observed to undergo attack in a wide range of pH from about 6 to at least about 9. During the reaction, that dye has been observed to undergo several color changes or shifts prior to a loss of color. Similarly, in the case of halogenated hydantoins, color shifting has been observed with C.I. Dye No. 42,090.
Although known to have general resistance to attack by hypochlorite ions, the dye of the present invention Colour Index Dye No. 52,035, has been found to be surprisingly resistant to hypohalite ions provided by dissociation of both halogenated hydantoin compounds and trichloroisocyanuric acid, notwithstanding the consequential formation of chloramines, over a broad range of pH. Similarly, said dye has been found to be resistant to attack in solutions containing calcium hypochlorite and ammonium ions, the presence of ammonium ions inducing the formation of chloramines. Moreover, Colour Index Dye No. 52,035 has been found not to stain porcelain, which is surprising in view of the staining tendencies of Methylene Blue, C.I. Dye No. 52,015, another blue dye in the triazine class.